Isotopic Abundance of Carbon Atoms

There exist two stable carbon isotopes in the natural world: 12C and 13C. The abundance ratio of 13C is about 1% of 12C.

According to experimental results, the relative abundances of natural isotopes are constant on the earth. The ratio of isotopes is called isotopic abundance. For carbon atom, the most abundant substance is 12C, and 13C atoms are observed at the rate of 12C.